1. Field of the Invention
My invention refers to facilitating and improving the selective process of obtaining a true color print.
Basically, color is our reaction to the wave length of light, as interpreted by the cones of the retina.
Modern color photography, printing and television rely on the concept that the eye responds to three basic colors: red, green and blue, ("additive primary colors"); other colors that we "see" are really combinations of the primary ones, being interpreted by the brain, as purple, brown, orange, etc.
Color photography and color printing all use "subtractive" systems. A color photograph works by reflecting light modified by dyes that act as filters, being built into three emulsion layers. Since our eyes respond to only three colors of light; red, green and blue, there is only need for three emulsion layers. By varying the amount of filtration in these three layers, all colors viewable in a color photograph are reproduced. The three filter colors in these layers, as well as in the color heads of modern enlargers are called "cyan," "magenta" and "yellow." These are the "subtractive primary colors" or "complementary colors." Each of the subtractive primaries consists of white light from which one of the additive primary colors: red, green and blue has been subtracted or removed.
Depending on the color reproduction process, e.g., making a print from a color negative or transparency, one of the complementary colors in the color head of the enlarger always remains constant, while the densities of the other two are varied to provide the correct filtration corresponding to the sensitivity of the respective layers in the emulsion of the paper.
Therefore, if we arbitrarily assign the variables X, Y and Z to the three complementary colors "cyan", "magenta" and "yellow," one of them will always remain constant while the others are varied during the process. Let Z be the constant factor, e.g., the complementary color "cyan" in printing from a negative or the complementary color "magenta" in printing from a transparency. To reproduce the correct color relationship in the final photograph, X and Y have to be in a certain relation to each other, as well as to the constant factor Z. Only one combination of these three factors will reproduce the right color on the emulsion. Even though the manufacturers of photographic paper give indications on the package as to what amount of filtration should be used for a batch of paper, the individual operator of color reproduction equipment always must resort to a "trial and error" procedure until he finally arrives at the right color combination.
This is known in the industry as a "ring-around", a procedure where all the possible deviations from a given filter combination are explored to finally arrive at the right combination.
With factor Z of a certain constant value, let us assume that the starting factors for Y and X are 0 and 0. In a "ring-around", there are eight (8) different possibilities for deviating from this neutral position; factor X can be increased or decreased, and factor Y can be varied in the same manner.
We will therefore arrive at eight different combinations of X and Y, apart from the neutral starting point. One of these new relationships between X and Y will be the correct--or approximately correct--combination for the overall relationship of colors required to reproduce the correct colors in the photograph. In other words, by starting from a given X/Y relationship and going into all eight directions of possible different X/Y relationships, the proper filtration values required for a correct color reproduction in the photographic print can be determined.
The ability to provide a NINE-position "ring-around" on one sheet of photographic paper for a very simple and quick evaluation of the correct color filtration is, in essence, the basic concept of this invention.
2. Description of the Prior Art
The following U.S. patents appear to represent the prior art with respect to my invention:
U.S. Pat. No. 3,588,248 FREUND 1971 PA1 U.S. Pat. No. 3,829,211 MITCHELL 1974 PA1 U.S. Pat. No. 3,944,364 PETRINI 1976 PA1 U.S. Pat. No. 4,095,892 THORNTON 1978 PA1 U.S. Pat. No. 4,108,548 HAWKINS 1978
None of the above cited patents appear to be directly relevant to the invented subject matter.
Furthermore, there is no present easel construction enabling the operator to produce a complete "ring-around" for evaluating the color quality of nine images on one sheet of photographic paper and in one single operation.
There are, in multiprinting, several devices which offer a set-up for printing of several images on one sheet of paper; however, none of them incorporates the smooth interaction and simple construction of components, as conceived in my invention.